U.S. stocks suffered their worst selloff in 2015 on Thursday as markets were buffeted by worries about a slowdown in global growth.

The broad-based rout, which saw the main indexes turn negative for the year, was marked by heavy selling in consumer-discretionary, technology, energy and media shares, with investors unloading stocks into the close of trading, intensifying the markets slide and pushing indexes to their lowest levels of the session. That may signal more unsettling moves ahead Friday.

“There is heightened uncertainty that began with yuan devaluation last week, while overall China’s growth is slowing faster than thought. This is weighing on confidence,” said Randy Frederick, managing director of trading & derivatives at Schwab Center for Financial Research.

The S&P 500
SPX, +0.31%
lost 43.88 points, or 2.1%, to 2,035.73, falling below a 200-day moving average, a key technical level. The benchmark index also turned negative for the year, ending 1.1% below its close at the end of 2014.

The Dow Jones Industrial Average
DJIA, +0.26%
shed 358.04 points, or 2.1%, to 16,990.69, its steepest percentage decline since Feb 3, 2014, and its lowest closing level, below psychologically significant 17,000 level, since the end of October.

Meanwhile, the tech-heavy Nasdaq Composite Index took the brunt of the Thursday’s thrashing,
COMP, +0.52%
ending the day off 141.56 points, or 2.8%, to 4,877.49, its steepest one-day decline since April 10, 2014.

The selloff comes about 24 hours after investors reacted badly to minutes that some investors read as taking a September rate increase off the table, but mostly delivered no clear guidance of the timing of the Fed’s first interest-rate increase in more than a decade.

The nervousness on Wall Street was apparent from a jump in the CBOE Volatility index
VIX, -2.53%
which has gained nearly 50% to 19 over the past three trading days. Meanwhile, U.S. Treasuries and gold rallied as investors sought havens.

“Technology and consumer discretionary, or momentum stocks are selling off, because they had performed pretty well recently and so have more room to fall during broader market selloffs,” Frederick said.

The Russell 2000
RUT, +0.35%
fell 30 points, or 2.5% to 1,172.54 and is now 9.5% below its peak in June.

“Investors are realizing that the reason for pushing back the timing of the first rate hike to December may be due to deflationary pressures from the rest of the world,” said Chris Gaffney, president at EverBank World Markets.

“Meanwhile, an overnight shock from emerging market currencies and a continued rout in oil prices, is prompting investors to flee equities and pile into havens such as Treasuries and gold,” Gaffney said.

Movers and shakers:Eli Lilly & Co.
LLY, +1.19%
shares jumped 5.4% after the drug maker along with Boehringer Ingelheim announced their diabetes drug Jardiance reduced risk of heart-related death, heart attack and stroke when added to standard treatment in a large trial.

Shares of Valeant Pharmaceuticals International Inc.VRX, +1.62%
fell 6.5% after the drug maker said it’ll buy Sprout Pharmaceuticals Inc. — the company that just won approval to sell the first drug that aims to boost a woman’s libido — for about $1 billion in cash.

Lumber Liquidators Holdings Inc.LL, -1.15%
jumped 8.9% after Cantor Fitzgerald lifted the price target on the hardwood flooring company to $18 from $15.

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